Routing Multicast Traffic

Routing Multicast Traffic
Up to this point, we have been discussing the host side of multicast. You have learned how hosts
interact with switches and routers to join multicast groups and receive the traffic. It is now time
to move on to discuss how multicast traffic travels across the Internet (or intranet) from a source
on a remote network to a local router and host.
Unicast data uses routing protocols to accomplish the task of getting data to and from remote
destinations. Multicast does the same, but it goes about it in a somewhat different manner. Unicast
relies on routing tables. Multicast uses a sort of spanning tree system to distribute its data.
This section describes the tree structures that can be implemented to enable multicast routing.
In addition to trees, several different protocol methods can be used to achieve the desired implementation
of multicast.